How to dynamically change the visible captions?
When working with the captions / text-track options, you can dynamically change the currently selected language (or set a default language) using following methods.
This method assumes that you are using text-tracks that are loaded with the manifest. If you add the text-track separately, you can just use this API: TextTrackDescription
Step-by-step guide
1. Create a new function inside the browser
Web SDK
function setLanguage(player, language) {
// Disable all text tracks that are currently active
player.textTracks
.filter(function (x) {
if (x.mode !== "disabled") {
return x;
}
})
.forEach(function (x) {
x.mode = "disabled";
});
// Enable the text track for a specific language. Note: Here we are searching the label. You can also do x.language for the ISO 3 letter language code.
player.textTracks.filter(function (x) {
if (x.label == language) {
return x;
}
})[0].mode = "showing";
}
iOS/tvOS SDK and Legacy iOS/tvOS SDK (4.12.x)
private func setLanguage(player: THEOplayer, language: String) {
let list: TextTrackList = player.textTracks
for i in 0..<list.count {
var textTrack: TextTrack = list[i]
if textTrack.label == language {
textTrack.mode = .showing
}
}
}
Roku SDK
In the following example we are iterating through all available text tracks. Once we found a track with a desired language, we simply set the mode to "showing". After that, we have to simply assign testTracks object to a proper THEOplayer attribute. This is all you have to do to make a desired text track visible. Of course, we can modify a visible text track during the video playback.
function setCaptionsLanguage(language as String)
textTracks = m.player.textTracks
for i = textTracks.count() - 1 to 0 step -1
if textTracks[i].kind = "captions" and textTracks[i].language = language then
if m.fullScreen then
textTracks[i].mode = "showing"
else
textTracks[i].mode = "hidden"
end if
else
textTracks[i].mode = "disabled"
end if
end for
'assignment of new roAssociativeArray is required because roku deep-copied roAssociativeArray through fields (pass-by-value)
'read more : <https://developer.roku.com/en-gb/docs/developer-program/performance-guide/optimization-techniques.md#OptimizationTechniques-DataFlow>
m.player.textTracks = textTracks
end function